The present invention relates to an apparatus for introducing measured or dosed quantities of pulverized or pulverulent materials into a carrier gas stream.
An apparatus for proportioning and extracting pulverized materials of the type herein discussed, has been disclosed in European Patent Application No. 0108319 as well as in Luxembourg Patent Application No. 84-462 corresponding to U.S. patent application Ser. No. 550,565, and Luxembourg Patent Application No. 84-780 corresponding to U.S. patent application Ser. No. 604,465, the two U.S. patent applications being assigned to the assignee hereof, all the contents of which are incorporated herein by reference. The invention described in European Patent Application No. 0108319 and the pending U.S. applications are particularly applicable to the operation of injecting solid fuels into a shaft furnace during a metal refining process.
In the dosing apparatus described in the above-mentioned patent applications, the propulsion fluid or carrier gas (usually consisting of air under pressure) passes through and leaves the dosing device in the axial direction, carrying along with it the pulverulent materials introduced through a lateral orifice. The current of pulverulent materials must therefore be deflected more or less at right angles when the pneumatic (entrained carrier gas) current is formed. This right angle deflection can be easily achieved in the case of certain small solid substances, such as coal dust (of which the grain size does not exceed 0.1 mm). However, as the granulometry of the particles increases, it becomes more difficult to achieve adequate deflection of the pulverulent materials. The problem is particularly acute in the case of calcium silicates (CaSi) injected into baths of steel during refining. In addition to the risk of premature wear to the dosing device, this deflection involves the alternate braking and acceleration of the pulverulent particles, resulting in a loss of speed and in a reduction of the quantity of material which can pass through the dosing device.